1. Field of the Invention
The present invention relates to an electric actuator. In particular, the present invention relates to an electric actuator in which a displacement member makes rectilinear motion under a guiding action of a spline guide mechanism using an involute spline.
2. Description of the Related Art
Electric actuators, which use a feed screw mechanism, have been hitherto used as a means for transporting a workpiece or the like. The electric actuator comprises a feed screw shaft which is coaxially connected, via a coupling member, to a drive shaft of a motor in a frame. A feed nut, which is provided for a displacement member, is screw-engaged with the feed screw shaft. A linear guide mechanism including, for example, a guide rail and a guide block which slides along the guide rail is provided in the frame. The displacement member is linearly guided along the feed screw shaft. An attachment section, which protrudes to the outside through a slit formed through the frame, is provided on one side of the displacement member. The attachment section is connected to a slide table.
In this arrangement, the feed screw shaft is rotated by the rotation of a motor. The rotary motion of the feed screw shaft is converted by the feed nut into the rectilinear motion. The displacement member is displaced in the longitudinal direction of the frame under the guiding action of the linear guide mechanism. Accordingly, the slide table is displaced, and thus the workpiece on the slide table is transported.
However, in the conventional electric actuator, when a heavy workpiece is placed on the slide table to transport the workpiece, the linear guide mechanism cannot absorb the load applied by the action of the gravity exerted on the workpiece in a circumferential direction about the center of the axis of the feed screw shaft, in a circumferential direction about the center of the horizontal line substantially perpendicular to the axis of the feed screw shaft, in a circumferential direction about the center of the vertical line substantially perpendicular to the axis of the feed screw shaft, and in a direction obtained by compositively combining the these directions.
As a result, the feed screw shaft is flexibly bent, and the sliding resistance is increased between the feed screw shaft and the feed nut.